The percentage yield tells you how close to the theoretical yield. The higher the percentge yield, the closer you are o the theoretical yield .
Percentage yield = Actual yield / theoretical yield * 100
Number of Moles and molar mass.
1 mole of an element is 6.022 * 10^23 atoms of that element. This gives a number in grams that is equal to the atomic mass of the element. for example Hydrogen has an atomic mass of 1(g) (approximately).
However molecular mass is different as some elements go around attached to eachother for example Hydrogen and Oxygen go around in 2s. So the Molar mass of Hydrogen is 2g and of Oxygen is 32g.
Relative atomic mass * Number of moles = Mass
Ideal gas equation
PV = nRT
P = pressure in pascals (pa)
V = volume in cubic metres (m^3)
n = amount of gas measured in moles (Mols)
R = the gas constant 8.31JK^-1 mol^-1
T = absolute temperature measured in Kelvin (K)